Gene expression can be regulated at many different levels, including at the level of protein synthesis. One of the principal mediators of translational control is the protein kinase DAI, which is activated by double-stranded RNA (dsRNA). When activated, DAI phosphorylates a protein synthesis initiation factor, eIF-2, resulting in the inhibition of protein synthesis. This kinase is part of the interferon induced anti-viral response and it may also subserve additional functions, both in infected and uninfected cells. The research proposed here aims, first, to discover the mechanism whereby DAI is activated by dsRNA, and how the small adenovirus RNA, VA RNA, prevents DAI activation, thereby rendering adenovirus infection insensitive to interferon. This requires an understanding of the structure of VA RNA and DAI, and of the nature of the interactions between DAI, VA RNA and dsRNA. A combination of biochemical and molecular genetic approaches will be used to achieve this aim. A second overall objective is to appreciate more fully the functions of DAI in infected cells, where it may also play a part in virus-induced translational selectivity, and in uninfected cells, where its functions are unknown. To address this objective, the subcellular localization and biochemical associations of DAI will be studied, additional DAI substrates will be sought and characterized, and the effects of DAI in vivo will be examined in both infected and uninfected cells. These investigations will throw light on the functions and control of this regulatory enzyme.